THE VEGETATION OF WOODLANDS. 13 



of the woods. Thus one finds the oak-woods of southern 

 England repeated essentially in the same form in the Yorkshire 

 Dales, in the south of Scotland and in the lower grounds of 

 northern Scotland, though some of the plants of the ground- 

 vegetation may be different. Again, some woods of Somerset 

 are almost identical with woods in East Anglia with a drier 

 climate, but in the Somerset woods, ferns are much more numerous 

 than in East Anglia. It is hardly necessary to point out that 

 in comparing the effects of climate over wide areas, the com- 

 parison ought to be made between woods at about the same 

 altitude above the sea. 



Turning now to the distribution of woodlands in belts at 

 different altitudes, we find a greater difference, but this cannot 

 always be put down to difference of climate, and, as described 

 later, may be due to soil. Wind is, however, a climatic factor 

 of great importance in forestry. Tree-growth ceases wherever 

 the wind attains such a force that the formation of young shoots 

 is prevented. The determination of this wind-zone must always 

 be considered in forestry. It cannot be defined as so many feet 

 above sea-level. The action of wind may be very marked on 

 the coast itself, and on a hill range it depends on the topo- 

 graphy. Hills can be grouped into long simple ranges or into 

 hill-masses. The Pentlands, Ochils, and Sidlaws, and parts of 

 the Pennines between Lancashire and Yorkshire are simple 

 ranges which branch little and enclose only short river valleys. 

 Representative hill-masses occur in the Lake District, in the 

 Southern Uplands of Scotland and in the Grampians. Compar- 

 ing these two types of hill-grouping, it will be found that the 

 hill-mass is much more favourable for afforestation than 

 the long simple range. The long narrow range has a narrow 

 watershed ridge and steep broken slopes, because wind and 

 atmospheric agents of erosion have full play ; the result is that 

 screes of loose stones or rocks occupy a large proportion of 

 the ground, and are generally unsuitable for the growth of 

 trees ; the wind has also full play, and few places are 

 sheltered enough for trees. On the hill-mass all this is 

 modified, and a greater part of the area consists of branching 

 valleys, rounded summits with broad intervening cols, and 

 gentle slopes completely clad with vegetation. Here wind and 

 erosion have less effect, the soil is less disturbed, and the 

 primitive vegetation remains. It is also the case on a hill-mass 



